The International Energy Agency cut its estimate for the amount of oil OPEC will need to pump in 2010 on a weaker demand outlook and as supply from outside the group rises by the largest annual amount in six years.

The Organization of Petroleum Exporting Countries will need to pump 28.7 million barrels a day to balance global oil demand and supply this year, the IEA said in its monthly market report today. That is 400,000 barrels fewer than estimated last month. The agency cut its estimate for total world oil consumption from 2008 through this year because of changes to historical data, BusinessWeek reports.

Iran and Malaysia have registered lower-than-expected oil demand in recent months, the IEA said, although China—the main driver of the growth in world oil consumption—was still seen logging robust demand.

The IEA, which acts as an energy watchdog for largely wealthy nations like the U.S., has been on the optimistic side about oil demand compared with other industry forecasters, Wall Street Journal says.